Production op dehydrated castor oil



Patented July 31, 1945 2,380,720 7 PRODUCTION OF DIHYDBA'IED CAS'IOB OIL Herman 8. Bloch, Riverside, 111., aasignor to. Universal Oil Products Company, corporation of Delaware Chicago, 111., a

No Drawing. Application Mar 2c, 1943, SerialNo. 488,562

5 Claims.

This invention relates to the treatment of castor oil to produce a modified oil having the properties of a drying oil.

One object of my invention is to eilect the conversion of castor oil in the presence of a solid catalyst from a non-drying oil to a material having drying characteristics.

Another object of my invention is the treatment of castor oil in the presence of a solid phosphoric acid catalyst to eflect removal of water from the ricinoleic acid groups present in the oil.

A still further object of my invention comprises treating castor oil to effect its dehydration to a drying oil which may be used alone or in admixture with other natural or synthetic dryin oils in the manufacture of paints, varnishes, or other coating materials, and in the preparation of synthetic resins. My process may also be adapted to produce an oil to be used in the production of lubricating oil, the reaction conditions being controlled so as to effect less dehydration than is desired for a drying oil product.

The dehydration of castor oil involves the splitting of water from the ricinoleic acid groups of the triglyceryl ester which comprises the principal constituent of said oil. In addition to the introduction of new double bonds into the glyccritic of ricinoleic acid, it is also desired to effect conjugation of the double bonds simultaneously with the dehydration, as it is known that the drying speed of oils is dependent upon the proportion of conjugated systems of double bonds in the oil molecule. As used here the term dehydration does not refer to the mere removal of water which may be present in the castor oil undergoing treatment, but is concerned solely with the removal of hydroxyl groups together with an adjoining hydrogen in the form of water from rici-' noleic acid or its triglyceride. and in so doing, introducing a second double bond into the acid molecule.

Present commercial processes for dehydrating castor oil are based chiefly on the use of liquid mineral acids such as sulfuric acid, sulfonic acids of aromatic hydrocarbons, acid esters or small quantities of acid salts of these mineral acids.

' I have now found that improved results may be obtained from an easily controlled process which involves employing a solid catalyst of the type described in, U. 3. Patent #l,993,5l3 to eil'ect to the point where chemical combination between the acid and the siliceous adsorbent takes place, while the. amount of free acid is reduced to a negligible proportion. Careful control of reaction conditions, including pressure, temperature, and space velocity, is also necessary tosecure optimum results. By employing the solid catalyst as herein set forth, the problem of separating the product from a liquid catalyst is avoided, while the catalyst itself may be easily regenerated and reused.

Broadly, my invention comprises treating a castor oil at dehydrating temperature in the r ence of a solid catalyst to eifect dehydration of the ricinoleic acid groups in said oil to octadecadienoic acid groups.

In one embodiment the present invention comprises passing castor oil over a solid phosphoric acid catalyst at pressures substantially below atmospheric and under carefully regulated conditions or temperature and space velocity so as to effect substantial dehydration of said oil.

In a more specific embodiment, my invention comprises heating castor oil in the presence of a precalcined solid phosphoric .acid catalyst at pressures substantially below atmospheric and under carefully controlled conditions of temperature and space velocity to effect substantial dehydration of the castor oil and to form an oil which is more completely miscible with mineral oils and which may be more readily combined with paint and varnish components.

I have found that operating at subatmospheric pressures increases the degree of dehydration,

especially to oleflnic rather than to etheric prod- I note. Lower pressures also reduce the oil absorption of the catalyst, so that there is little loss of desired product and regeneration of the catalyst is thereby simplified. The precalcined 4o catalyst may be regenerated, after, deactivation, by simple combustion of deposited carbonaceous material and then employed in the calcined state for (further pr. with no loss of activity.

In the operation of my process, the castor oil is passed under'reduced pressure through a packed reactor containing a bed of the solid catalyst at a liquid hourly space velocity'of from about 1 to about 10. The oil is heated'to temperatures of between 200 and 326 C. and preferably bedehydration of the castor oil. The cataly t comprises a phosphoric acid, and preferably the orthophosphoric acid, mixed with an adsorbent material of .a predominantly siliceous character.

The preferred adsorbent is k'ieselguhr. The lidllld acid and the adsorbent are mixed and heated tween 250' C. and 300? C. I Temperatures higher than 325C. are avoided as theytend to cause cracking and degradation of the oil as well as dehydration. The pressure is maintained at about 50mm. of mercury or less. Preferred pressuresemployedarelessthaniiomm. Atpressures of about 50 mm. of mercury the amount of 

